prefers-reduced-transparency Media Query

[lukewarlow]

Description

Following on from Interop 2023s Media Queries 4 focus area, it would be good for some of Media Queries 5 to be focussed on next. This request is specifically for the prefers-reduced-transparency media query, this has shipped in Chromium recently.

Specification

https://drafts.csswg.org/mediaqueries-5/#prefers-reduced-transparency

Open Issues

No response

Tests

https://wpt.fyi/results/css/mediaqueries/prefers-reduced-transparency.html

Current Implementations

• Blink
• Gecko
• WebKit

Standards Positions

WebKit: WebKit/standards-positions#145

Gecko: mozilla/standards-positions#851

Gecko Intent to Prototype: https://groups.google.com/a/mozilla.org/g/dev-platform/c/l410J8odZjA/m/JdWVMNtSAQAJ

Browser bug reports

No response

Developer discussions

No response

Polls & Surveys

No response

Existing Usage

No response

Workarounds

No response

Accessibility Impact

This will help sites to honour user preferences for reduced transparency.

Privacy Impact

This exposes a new fingerprinting bit (like all user preference media queries)

Other

There's a PR to webkit that implements this, and Firefox has an implementation behind a flag.

[cookiecrook]

Although I originally proposed this media feature, I'm not sure what can be done about this for Interop 2024 given that abuse of matchMedia() hasn't been addressed with some of the user preference (prefers-*) media features... And, unlike the users with vestibular impairments clamoring for prefers-reduced-motion, we're not seeing the same amount of user need. Though I acknowledge transparency contributes to reduced readability among low vision users, many are making do with existing features such as font size increase and prefers-contrast.

I'd love to see this media feature ship, but I am concerned about proposing it for Interop 2024 given that there is an open debate about the privacy implication.

Additional context on why this isn't implemented in WebKit yet found in WebKit Position #145 and CSS #8651 (quoting from the latter):

Note on Fingerprinting

[ Several proposed media features, including this one] are subject to changes based on the
outcome of WebKit/standards-positions#145 and other related privacy issues. We debated
not proposing w3c/csswg-drafts#8651 until after privacy issues with @media/matchMedia()
had been resolved, but decided to propose it here anyway to further the discussion.

[lukewarlow]

That's absolutely fair. I was wondering if instead of proposing this it might be better to propose a research focus for finding a solution to the privacy issue (such as making certain media features opt in to exposing the true value)

[lukewarlow]

See #515

[lukewarlow]

Closing this in favour of discussing mitigations in the csswg